The YouTube Ratings add-on for Google Chrome shows the likes and dislikes bar for every video thumbnail on the YouTube website to help you get an idea of the overall rating of the video before watching it.
It adds colored bar near the video thumbnails – red represents dislikes while green color is for likes – and the longer the red bar, the more likely it is that the corresponding video isn’t worth your time. If the video owner has disabled ratings for a particular video, a gray bar is displayed.
You can also configure the extension to automatically highlight the best videos on any YouTube page by enclosing the video thumbnail in a blue box. This works for both search results on YouTube as well as related videos.